Introduction: Adolescent idiopathic scoliosis (AIS) is a three-dimensional spinal deformity characterized by lateral curvature, vertebral rotation, and sagittal imbalance. It affects 2–4% of adolescents, predominantly females (7:1 ratio). Progressive deformity can cause respiratory dysfunction, chronic pain, and psychosocial distress. Developing effective conservative treatments remains a major challenge in orthopedic rehabilitation. This study aimed to evaluate the effectiveness of combined Schroth therapy and 3D-Chêneau bracing in managing AIS, focusing on sagittal alignment, postural control, and functional improvement. Material and Methods: A prospective quasi-experimental study was conducted with 60 adolescents (mean age 13.3 ± 1.6 years) diagnosed with AIS (Cobb angle 20°–47°). The intervention consisted of two phases: an intensive 3-week supervised Schroth exercise program (21 sessions) followed by continued home exercises combined with a custom 3D-modified Chêneau brace. Assessments were performed at baseline, 4 weeks, 3 months, and 6 months. Primary outcomes included sagittal balance (mm) and sagittal index (mm), evaluated by standardized plumb-line analysis. Results: After six months, significant improvements were observed in sagittal alignment (p < 0.001). Sagittal balance increased toward the physiological reference (~20 mm), indicating improved postural symmetry and trunk stability. Sagittal index values reflected curve-specific and localization-dependent adaptations, particularly in thoracic deformities. Conclusion: Combined Schroth therapy and 3D-modified Chêneau bracing effectively enhanced sagittal spinal alignment in adolescents with AIS. This integrated conservative approach demonstrated measurable improvements in physiological balance and postural organization, supporting its role as a functional, noninvasive intervention for AIS management.